Large quantities of an exhaust gas and waste water containing NH3 are discharged from a variety of industrial plants such as semiconductor factories, resulting in a variety of bad effects such as odor environmental pollution, and deterioration of water quality. Particularly, in recent years, eutrophication of sea water such as generation of red tides due to NH3 contained in industrial waste water becomes a social problem; and in this respect, laws for severely restricting NH3 concentration in waste water are going to be developed. For this reason, a variety of studies and developments are made on a technology for defusing NH3; and the following technologies are going to become mainstreams as a treating technology for exhaust materials containing NH3.
Namely, a method for catalytically oxidizing NH3 with a catalyst is known as a technology for decomposing NH3 in a vapor phase, while a method for catalytically oxidizing NH3 by using the above-mentioned catalyst after transferring NH3 in waste water to a vapor phase in an aeration tower or a stripping tower is known as a technology for decomposing NH3 contained in industrial waste water. These technologies are ones drawing attention as a method for using a multifunctional catalyst having a denitration function due to a denitration active component and a function of oxidizing NH3 to form a nitrogen oxide (NOx) due to a noble metal component in combination in the catalyst, whereby, several % of NH3 may be converted efficiently into harmless nitrogen (N2), for example.
Patent document 1: Japanese Patent Application Laid-Open No. 5-146634
Patent document 2: Japanese Patent Application Laid-Open No. 2000-317272